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I have a 1999 grand Cherokee got A p1391 car not running bad…

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I have a 1999 grand...
I have a 1999 grand Cherokee got A p1391 car not running bad just a 5 sec crank once and a while so I replaced both crank and cam sensors now has A bad misfire on take off and still gives a p1391 code any answers would be appreciated it's a 4.7 v8
Submitted: 10 months ago.Category: Jeep
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Answered in 2 minutes by:
10/1/2017
Jeep Mechanic: Dan, Technician replied 10 months ago
Dan
Dan, Technician
Category: Jeep
Satisfied Customers: 26,041
Experience: Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Jeep Mechanic: Dan, Technician replied 10 months ago

The next likely things would be wiring or PCM. Next step would be to use a scope to monitor crank/cam signals to see if they are in sync, if not problem would be timing chain. If they are in sync and both working properly then PCM would be the problem. If one of them are erratic then you would want to check wiring/connector going to that sensor. Let me know if you have more questions, thanks.

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Customer reply replied 10 months ago
I did buy my sensors from advance auto does that become an issue
Jeep Mechanic: Dan, Technician replied 10 months ago

Yes that is very possibly a issue, before digging too deep returning those sensors and buying OEM sensors would probably be a good idea. You can get them off ebay for about half of what dealer would charge. Let me know if you have questions or would like links to buy. Thanks.

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Customer reply replied 10 months ago
Ok just frustrated the car ran fine no issues I had to get it inspected and it failed for the code 1391 without the light on you wouldn't know anything was wrong changed sensors and pow misfire on takeoff I would not thank pcm or timing chain because it ran fine before but I don't know
Jeep Mechanic: Dan, Technician replied 10 months ago

If replacing sensors made it run worse then I'd agree with you on aftermarket sensor being problem. Let me know how it goes or if you run into questions, you can reply to this answer at any time without additional fees. Thanks.

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Customer reply replied 10 months ago
Ok thanks Dan
Jeep Mechanic: Dan, Technician replied 10 months ago

No problem, I'm happy to help. Have a good evening.

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Customer reply replied 10 months ago
Dan I put the old cam sensor back in and drove it no misfire but light is still on of course
Jeep Mechanic: Dan, Technician replied 10 months ago

I think replacing with OEM sensors will probably take care of problem. It is a guess but only way to get around guessing is scoping the sensors which is usually something a DIY person doesn't have access to.

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Customer reply replied 10 months ago
Hi Dan just wanted to let you know that I got a diagnosis on my jeep bad pcm you can clear the code 1391 the light will go off but it never clears the computer turned the switch off and turned it back on but didn't start the engine and the obd tool still showed the code then if you crank it the light comes back on on the second crank cycle every time
Jeep Mechanic: Dan, Technician replied 10 months ago

Here is a website to buy one programmed to vin, let me know if you have questions. Thanks.

-

http://www.fs1inc.com/jeep-ecu-ecm-pcm.html?make=100&model=159&year=132

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Jeep Mechanic: Dan, Technician replied 9 months ago

Ever get it figured out? Please do not forget to rate answer. Thanks.

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